(a) Field of the Invention
The present invention relates to a transmission mounting unit for a vehicle. More particularly, the present invention relates to a transmission mounting unit for a vehicle for connecting a vehicle body and a transmission to efficiently attenuate a vibration generated by the transmission.
(b) Description of the Related Art
In general, an engine vibrates due to periodical changes in a central position caused by up and down motions of a piston and a connecting rod and a rotary motion of a crank shaft, an inertial force of the up and down motions of the piston and the connecting rod, and a torque of the crank shaft.
A transmission connected to the engine structurally always receives a vibration so that a torque of the engine in accordance with a driving state of a vehicle is increased or reduced.
Therefore, when the transmission is mounted in a vehicle body, it is necessary to devise an appropriate vibration insulating unit so as to improve a ride comfort of a passenger.
The engine and the transmission are referred to as power trains, and are supported by and mounted in the vehicle body by an engine mounting unit and a transmission mounting unit, respectively.
In a conventional art, insulators for insulating a vibration are applied to the engine mounting unit and the transmission mounting unit, respectively. However, it is difficult to appropriately absorb a complex vibration that appears in a wide frequency band only by use of the insulators.
To be specific, there are limitations on reducing dynamic characteristics of the engine and the transmission in an idle region only by use of the insulators. When a loss coefficient is reduced to reduce the dynamic characteristics, driving performance of a vehicle may be deteriorated.
In order to address such a drawback, a cone fluid encapsulation mounting unit that effectively absorbs a vibration through an operation fluid filled therein is used as the conventional engine mounting unit. However, due to space restraints, it is difficult to use the cone fluid encapsulation mounting unit as the transmission mounting unit. On the other hand, when a hydro bush is applied to the transmission mounting unit, static loads of the power trains are operated so that an excessive gap is formed between a top of a core and an outer pipe. Therefore, a ride comfort is deteriorated and durability may be deteriorated.
Therefore, it may be desirable to provide a method of forming a gap on the insulator between the core and the outer pipe and bonding an additional stopper formed of a rubber material through the gap to reduce displacements of the insulators, to increase durability, and to control a displacement of the transmission.
However, when the additional stopper is provided, constituent elements may be increased, an assembly process may be complicated, and manufacturing cost may be increased. In addition, as the additional stopper is bonded through an adhesive, the stopper is vulnerable to heat and contamination and may be separated from the insulators. Therefore, noise, vibration, and harshness (NVH) performance and durability of a vehicle may be deteriorated, and a vehicle dependability study (VDS) index may be reduced.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.